From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-bugs-return-382424-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 31437 invoked by alias); 3 Feb 2012 13:29:23 -0000
Received: (qmail 31428 invoked by uid 22791); 3 Feb 2012 13:29:23 -0000
X-SWARE-Spam-Status: No, hits=-2.9 required=5.0	tests=ALL_TRUSTED,AWL,BAYES_00
X-Spam-Check-By: sourceware.org
Received: from localhost (HELO gcc.gnu.org) (127.0.0.1)    by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 03 Feb 2012 13:29:11 +0000
From: "vincent-gcc at vinc17 dot net" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/52106] warning for useless assignments
Date: Fri, 03 Feb 2012 13:29:00 -0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: changed
X-Bugzilla-Watch-Reason: None
X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Keywords:
X-Bugzilla-Severity: enhancement
X-Bugzilla-Who: vincent-gcc at vinc17 dot net
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Priority: P3
X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org
X-Bugzilla-Target-Milestone: ---
X-Bugzilla-Changed-Fields: Status Resolution Summary
Message-ID: <bug-52106-4-PYBtaqO07n@http.gcc.gnu.org/bugzilla/>
In-Reply-To: <bug-52106-4@http.gcc.gnu.org/bugzilla/>
References: <bug-52106-4@http.gcc.gnu.org/bugzilla/>
X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/
Auto-Submitted: auto-generated
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc-bugs.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc-bugs/>
List-Post: <mailto:gcc-bugs@gcc.gnu.org>
List-Help: <mailto:gcc-bugs-help@gcc.gnu.org>
Sender: gcc-bugs-owner@gcc.gnu.org
X-SW-Source: 2012-02/txt/msg00358.txt.bz2

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D52106

Vincent Lef=C3=A8vre <vincent-gcc at vinc17 dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |
            Summary|missing                     |warning for useless
                   |-Wunused-but-set-variable   |assignments
                   |warning with the a =3D b =3D    |
                   |... construct               |

--- Comment #2 from Vincent Lef=C3=A8vre <vincent-gcc at vinc17 dot net> 20=
12-02-03 13:28:39 UTC ---
Then there should be another warning. So, this is a request for a warning f=
or
assignments that are obviously useless (thus maybe a typo in the code or old
code that could be removed...). It should cover variables set but not used
outside the full expression where they are set. The code

int foo (void)
{
  int a, b;
  a =3D b =3D 0;
  return a;
}

gives an example. It could be written:

int foo (void)
{
  int a;
  a =3D 0;
  return a;
}

"a =3D b =3D ...;" is generally used as a shortcut for "a =3D ...; b =3D ..=
.;", and if
it isn't (because the behavior would be different at compile time or at run
time), there should be a warning against this construct.